Using the experimental data below, calculate the weight percent of Vitamin C in
ID: 908037 • Letter: U
Question
Using the experimental data below, calculate the weight percent of Vitamin C in the unknown. Report a relative standard deviation.
Standardization of Thiosulphate Solution mass of KIO3 + weighing vial / g 24.5882 mass of weighing vial / g 23.4956 V KIO3 / mL 500.0 V KIO3 per titration / mL 50.00 trial 1 2 3 Initial burette reading / mL 0.12 0.08 0.10 Final burette reading / mL 39.16 39.10 39.16 Determination of Vitamin C Content mass of sample / g 2.6158 Volume of Vitamin C solution / mL 250.00 Aliquot Volume of Vitamin C solution / mL 25.00 trial 1 2 3 Initial burette reading / mL 0.06 0.14 0.10 Final burette reading / mL 26.22 26.34 26.28 Molar Mass Vitamin C 176.13 Correct Result Average mass Vitamin C per g of sample / g 0.340 %RSD 0.2Explanation / Answer
1) Standardization of Thiosulphate Solution
Mass of the KIO3 = 24.5882g - 23.4956 g = 1.0926 g
No. of mole = 1.0926g / (214g/mole) = 0.00511
Molarity of KIO3 = 0.00511 mole / 0.5 L = 0.1021 M
We know that M1V1 = M2V2
Molarity of Thiosulphate Solution M1 = 0.1021M x 50 ml / (39.16-0.12) ml = 0.1308 M
Determination of Vitamin C Content:
Use the dilution formula M1V1/n1 = M2V2/n2 (n2 =3)
Vitamin C Molarity M1 = 0.1308 M x (26.22-0.06) ml / (25 ml x 3) = 0.0456M
No. of moles of Vitamin C in 250 ml = 0.0456 M x 0.250 L = 0.0114 moles
Weight of Vitamin C = 0.0114 moles x 176.13 g/mole = 2.0093 g
Hence the weight percent of Vitamin C in the unknown = 2.0093 g * 100 / 2.6158 = 76.81 %
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